6mm ARC - Practical Reloading

[David Milisock]

As per SAAMI, ie 52,000 psi. Here's a view by White Oak Armament as to why 0.440" diameter case-head designs (ie as per the Grendel and ARC) aren't suitable in their view for the AR-15 bolt.

https://www.whiteoakarmament.com/blog/hornady-s-new-6mm-arc.html

Agree with White Oak or not, it's obvious that great care needs to be taken with handloads for these cartridges when loading for the AR-15 to avoid rapid bolt wear and/or failure.

This doesn't apply to bolt actions, hence the 62,000 psi Pmax allowance for this type. The case is extremely strong - the limitations come from bolt strength and designs.

The 2 year old White Oak Armament posting in terms of long life viability of the 6MM ARC at 52,000 PSI (in my opinion) has been confirmed.

The 52,000 PSI limit for AR15 loading for the 6MM ARC was something we were ALWAYS INFORMED OF, I love handloading and shooting but I won't blame a design that I abuse for failure.

The concept was as lightweight small arm (AR15) with improved performance over the 5.56 x 45 NATO in close and at extended ranges for special forces. That goal has been achieved.

However in terms of the AR user in my opinion people have screwed with a system that operates much closer to the limits than the 5.56 x 45 NATO version.

All the rifles that I have seen that have failed have two base causes for failure, one; they were built by people who experimented with adjustable gas systems, gas system lengths different than the designd, gas port size variations, light weight bolt carriers, various buffer systems. All which affect the timing ergo the pressure on the locking system during extraction and therefore wear on that mechanism. When a system operates closer to its maximum design limits mechanical changes risk failure.

The second issue is (in my opinion) is a lack of conservative reloading practices. Rarely do you see a handloader testing their loads for pressure. They use indicators not actual pressure guages. I see powders and projectiles being used in the AR platform that were not used by the original developers. I have done minimal testing but only with the projectiles used by Hornady and only with the LeverEvolution powder used by Hornadyfor the heavyweight projectiles.

Because of some health issues and my need to clear my head from medication cool weather had set in and my testing had to stop. Now this summer it will start again, watching closely the velocity of every round, extraction parameters and case wear compared to factory control ammunition at high temperatures.

Since the introduction Hornady now has developed some light projectile gas gun loads I suggest very conservative loading processes.

There have been no abnormal wear and or stoppage issues reported by the agencies that adopted the 6MM ARC in the AR 15 platform, in my opinion the general public adopting more closely controlled manufacturing, assembly and loading techniques (over those used by many of those buildings the 5.56 x 45 versions) will result in very positive results.

The bolt action players have at it.

 

[David Milisock]

The AR-15 was designed for the smaller diameter case. Increasing the diameter, as in the ARC, puts more force on the lugs (case has more area so more force on bolt). Something similar happens for bolt actions and Lapua size cartridges, you need bigger size with bigger lugs or there will be setback/failure.

Exactly, it's not like we don't know it going in. I don't have the facilities to test design parameters like Hornady and the rifle manufacturers that participated in the design have. Luckily all I have to do is follow their guidelines CLOSELY and it will all work out well.

 

[243Mendoza]

....

There have been no abnormal wear and or stoppage issues reported by the agencies that adopted the 6MM ARC in the AR 15 platform...

Are you in contact with the agencies using the 6ARC?

 

[Retired shooter]

Thank you Gentlemen for all the information, however you are definitely giving ma a warm and fuzzy feeling about my new upper build. !

 

[Gtscotty]

Oh Lord, the WOA article (subtext: "Why our 6mm WOA is totally better than this new 6mm ARC") rides again. I don't really understand all the pearl clutching around loading for the ARC. It's really very straight forward, stay within Hornady's load data for LVR, CFE223 or AA2520 if you want top safe velocities with heavy bullets. Some temp stable powders give good velocities with lighter bullets, but on the heavier end powders like Varget will be substantially slower than the three previously mentioned. If you try to push over book loads, expect lower bolt life. The only guy I've read about on another forum that was going through bolts (like 3) was supposedly trying to match LVR velocities with Varget... Don't do that in a gas gun and you should be fine.

Honestly the more I shoot my ARCs the more I like them. I just started working loads for my Ruger SFAR, and shooting it i'm struck by how much nicer to shoot my lighter hunting ARC is, with better external ballistics to boot. Some of it is the longer gas system on the ARC, but altogether the package just runs better, doesn't shred brass, isn't very gassy, is very quiet suppressed, easy to shoot well and accurate.

 

[Retired shooter]

Thank you Gtscotty, makes me more comfortable, just got Lever today, still waiting on the uppr.
Eagerly waiting.

 

[David Milisock]

Are you in contact with the agencies using the 6ARC?

I'm not in personal contact with anyone serving in special teams. I've researched the cartridge in the AR platform intensively. I didn't want to buy a pig in a poke! There have been in the past 3 videos from (reasonable sources) where special forces testing was mentioned with no negative comments. The topics was specifically bolt wear, if memory serves it was in mid 2021.

The time table has the testing production runs of the REC7 and ammo in June 2020, I believe. Barrett delivered the first batch in 2020 and Hornady the ammo, Barrett then announced that they would offer civilian REC7's after their government commitments were through, in early 2022 I read that initial order was complete but no civilian availability for their rifle yet. I suspect that Barrett is building an additional run of rifles has Hornady had an additional contract for ammo and the testing was completed in 2021.

 

[David Milisock]

Oh Lord, the WOA article (subtext: "Why our 6mm WOA is totally better than this new 6mm ARC") rides again. I don't really understand all the pearl clutching around loading for the ARC. It's really very straight forward, stay within Hornady's load data for LVR, CFE223 or AA2520 if you want top safe velocities with heavy bullets. Some temp stable powders give good velocities with lighter bullets, but on the heavier end powders like Varget will be substantially slower than the three previously mentioned. If you try to push over book loads, expect lower bolt life. The only guy I've read about on another forum that was going through bolts (like 3) was supposedly trying to match LVR velocities with Varget... Don't do that in a gas gun and you should be fine.

Honestly the more I shoot my ARCs the more I like them. I just started working loads for my Ruger SFAR, and shooting it i'm struck by how much nicer to shoot my lighter hunting ARC is, with better external ballistics to boot. Some of it is the longer gas system on the ARC, but altogether the package just runs better, doesn't shred brass, isn't very gassy, is very quiet suppressed, easy to shoot well and accurate.

I waited 50 years for the AR to be made into a useful general purpose rifle, the 6MM ARC made that happen. I thought maybe the 6.8 SPC or the 6.5 Grendel would fill the bill but I tried and no.

Simply the AR in 6 ARC is exactly as you say.

 

[86cookiemonster]

I waited 50 years for the AR to be made into a useful general purpose rifle, the 6MM ARC made that happen. I thought maybe the 6.8 SPC or the 6.5 Grendel would fill the bill but I tried and no.

Simply the AR in 6 ARC is exactly as you say.

i am of the same opinion.

 

[Retired shooter]

i am of the same opinion.

Guys
I was told this afternoon by a fellow that seems to be very knowledgeable about powders that the Leverevolution powder available to the public is not the same as Hornady used in the 6 ARC as some have stated.

He did show me in a 2023 Lyman reloading book about Alliant Pwr. Pro 2000 MR. Says a lot of guys are using it in the .224 Valk.

From all you experienced 6 ARC guys. Any of you have knowledge about the Alliant powder. I have used several different types for pistols. What about use for the 6ARC.?

BILL

 

[Gtscotty]

Guys
I was told this afternoon by a fellow that seems to be very knowledgeable about powders that the Leverevolution powder available to the public is not the same as Hornady used in the 6 ARC as some have stated.

He did show me in a 2023 Lyman reloading book about Alliant Pwr. Pro 2000 MR. Says a lot of guys are using it in the .224 Valk.

From all you experienced 6 ARC guys. Any of you have knowledge about the Alliant powder. I have used several different types for pistols. What about use for the 6ARC.?

BILL

I'd guess that Hornady uses a non-canister powder in their factory loads for the ARC if that's what you mean, that's the case for most factory loads. The Leverevolution powder that's in their published load data is definitely the same as the canister powder sold under the same name though. Haven't used 2000 MR, but it's in the Hornady manual and looks like it should work well.

 

[Retired shooter]

From what was explained to me , the Hornady factory load powder is different powder, as compared to the Leverevolution powder the public can purchase. Yes the lever listed in reload manuals is the same as what we purchase. Hogdon closed till after the first of the year, already tried calling.
Have also ordered new Lyman reloading manual. This is what I learned this afternoon.

 

[Retired shooter]

Lever is #141 on the burn chart, with the Alliant being #143. Will have to check my load books to see if the load data is there for the Alliant. Wondering if anyone had already used or tried the Alliant powder, it is a ball powder.

 

[Gtscotty]

Lever is #141 on the burn chart, with the Alliant being #143. Will have to check my load books to see if the load data is there for the Alliant. Wondering if anyone had already used or tried the Alliant powder, it is a ball powder.

Just in case you haven't seen it, Hornady published the attached gas gun load data to their website when they introduced the 6mm ARC.

 

[Retired shooter]

Thank you Sir.
How does the pressure relate comparing the two powders as they are close to the same charge weight, when using the same grain bullets.

Thanks.

 

[Retired shooter]

Is there any published data in regards to powder pressures. Where does one look.?
Never had to be this concerned before.

Thank you

 

[Gtscotty]

Is there any published data in regards to powder pressures. Where does one look.?
Never had to be this concerned before.

Thank you

I don't understand what you're confused about? The H load data above is all 52ksi or under, SAAMI compliant data, so good for gas guns. Hornady put out other data that higher the SAMMI pressure specs for 6mm ARC that's meant to only be used in bolt guns, and is clearly labeled as such.

 

[86cookiemonster]

maybe i missed it in the conversation, I'll admit it I am only half listening... where did we find out that hornady is using Leverevolution in the 6arc?

 

[David Milisock]

maybe i missed it in the conversation, I'll admit it I am only half listening... where did we find out that hornady is using Leverevolution in the 6arc?

I would say the use of LeverEvolution powder was listed in articles as the powder used for developing the cartridge and the rifles way back in 2020. I remember reading it and I also had early charts done on velocity verses barrel length that are not available anymore.

They currently have load charts and barrel velocity charts but they are not the ones you can download now.

I have no idea if Hornady still uses LeverEvolution or not but I certainly remember reading that it was used in developing the systems. I do know the most recent load data tables are different now.

What I noticed is that CFE charges were reduced in the new data. The original data only listed heavy 108 projectiles.

 

[Retired shooter]

I don't understand what you're confused about? The H load data above is all 52ksi or under, SAAMI compliant data, so good for gas guns. Hornady put out other data that higher the SAMMI pressure specs for 6mm ARC that's meant to only be used in bolt guns, and is clearly labeled as such.

My question was definitely not phrased correctly .
I am aware of the load data provided in the assorted load books.The load books show a safe working pressure of 52,000 of pressure and develop xxx fps of velocity per xxx number of grains of powder for that projectile. I am aware of and understand why the difference between gas guns and bolt action . I also understand many factors relate to velocity of a projectile.

Is there a testing lab that has data showing the (actual) produced pressure of Powder A @ X number of grains ,and the (actual) produced velocity for test projectile

A comparison chart with equal test parameters that shows Powder A @ 25 gns.produced 50 thousand psi of pressure @ 2500 ft per second velocity to projectile weighing 100 gn. with a impact force of. xxx ft lb at 100 yards

Powder B @25 gns produced 42,500 thousand psi. @ 2450 ft per second to the 100 gn. projectile. with impact force of xxx ft lb.
The load books, and charts are to me a generic listing of what is available.

Does such information exist, available to, we the people, or is it proprietary , and released on a need to know basis. This is just my in depth thoughts on the subject, ( am I trying to pick the fly crap out of the pepper) and need to be concerned with other factors more under my control.

Thank you.